Along with the commercialization progress of electric vehicles, a vehicle-mounted charger of the electric vehicles has become one of important components in the electric vehicles.
There are many methods for outwardly discharging from the whole vehicle via the vehicle-mounted charger. A monophase H bridge off-grid conversion control method is mostly adopted in related arts, which includes a dual-polarity control method and a mono-polarity control method.
However, when the dual-polarity control method is adopted, four switch transistors in an H bridge are all in a high frequency ON/OFF state, resulting in higher switching loss and larger heat loss. When the mono-polarity control method is adopted, although the heat loss of the switch transistors that is generated when the dual-polarity control method is adopted can be solved to some extent, the four switch transistors in the H bridge are controlled according to a fixed manner during a charging process or a discharging process of the whole vehicle, some switch transistors in the H bridge need to be switched off with current. The overheat problems of the switch transistors switched off with current are not effectively solved.
Therefore, regardless of whether the dual-polarity control method or the mono-polarity control method is adopted, the heating problems of the switch transistors in the H bridge cannot be effectively solved, and the service life of the switch transistors is affected.